Speedometer Calibration

[1999RedXLT]

I checked my Speedometer/Odometer calibration last weekend and it was off somewhat. I haven't run the numbers yet, but before I change anything I'd like to make sure I understand what I'm doing.

I have a Gryphon with canned tunes on a 1999 F-150 4.6L. Haven't ordered my custom tunes yet. I loaded and am running the towing tune, having tried the transmission only tune for a day or two. I HAVE NOT entered the custom parameters menu.

As I understand it, the Gryphon has the ability to change the speedometer calibration. I think this is done by changing the tire size. I think that changing the tire size will change all of: the Gryphon speedometer, the dashboard speedometer and the main and trip odometers.

1. Assuming all of the above is correct (?), and I am running the canned towing tune, what tire size is being used? The original tire size stored in the VID(?) area of the ECM, or a default number that is loaded with the canned tune? I'm asking because my odometer is off now but I never checked it before installing the Gryphon.

2. How can I determine what number the Gryphon is using currently in the canned towing tune?


3. Assuming I can get that number, I presume I can adjust it by the same percentage that the odometer is off and that should correct the odometer and speedometer, right?

Thanks for helping the newbie.....

Al